Active substance supply system for an agricultural sprayer

ABSTRACT

An active substance supply system for an agricultural sprayer has a main liquid circuit which includes a reservoir for a main liquid and permits circulation of the main liquid, where the main liquid circuit includes one or more distribution sections which are each configured to distribute to several dispensing elements a spray liquid to be dispensed, and a feed system which is connected to the main liquid circuit and in which the main liquid is mixed with at least one separately supplied active substance to form a liquid active substance mixture, where the active substance supply system is configured to introduce the active substance mixture into the one or more distribution sections at several places.

The invention relates to an active substance supply system for anagricultural sprayer according to the preamble of claim 1, anagricultural sprayer according to the preamble of claim 12, and a methodfor dispensing a spray liquid according to the preamble of claim 13.

Agricultural sprayers are known for dispensing spray liquid ontoagricultural land and operate with a so-called direct feed system withwhich active substances can be partially dispensed. Respective directfeed systems permit the addition of active substance to a main liquidduring the dispensing process, so that the need for stockpiling largequantities of a liquid active substance mixture composed of the mainliquid and the active substance is not necessary. Direct feed systemsalso permit the adjustment of the quantity of active substance andtherefore the adjustment of the mixing ratio of the spray liquid to bedispensed during the dispensing process.

Generic active substance supply systems regularly operate with a mainliquid circuit which comprises a reservoir for the main liquid andpermits the main liquid to circulate. The main liquid circuit usuallycomprises one or more distribution sections, each of which is configuredto distribute to several dispensing elements, such as spray nozzles, aspray liquid to be dispensed.

An active substance supply system operating according to the principleof direct feed is known, for example, from publication DE 10 2004 047585 A1. The publication proposes the use of a premix container in whichthe active substances are pre-diluted with the main liquid. Thepre-diluted active substance mixture is then conveyed to the linkage andagain mixed with the main liquid to form the spray broth to bedispensed.

In addition, publication DE 10 2006 059 193 A1 describes a system fordirect feed of active substances into a main liquid already conveyed tothe linkage. The active substances are pre-diluted and then diluted in amixing chamber with the carrier liquid to the desired concentration.

Publication DE 10 2006 045 450 A1 also describes that the circulation ofliquid within the linkage can be used for faster distribution of theactive substance via the linkage.

With regard to direct feed, however, there is still the problem that aso-called delay period arises until the fed active substance or thedesired liquid active substance mixture is present at all dispensingelements. Due to the longer flow path, the liquid active substancemixture is first present at the dispensing elements that are at theshortest distance from the feed point. With increasing distance of adispensing element from the feed point, the delay increases until thedesired active substance mixture is present at the respective dispensingelement.

The object of the present invention is therefore to reduce the delaytime of active substance supply systems having a direct feed, so thatadded active substance is present at the dispensing elements morerapidly.

The object is satisfied with an active substance supply system of thetype mentioned above, where the active substance supply system accordingto the invention is configured to introduce the active substance mixtureinto the one or more distribution sections at several places.

The invention makes use of the realization that the flow paths for theactive substance mixture, for example, to external dispensing elements,are significantly shortened when the active substance mixture isintroduced at several places into the one or more distribution sections.Due to this shortening of the flow paths, the active substance mixtureis already present at all dispensing elements after a shorter period oftime, so that the delay time is significantly reduced.

The distribution sections can be, for example, the partial widths of asprayer, each of which comprises a group of dispensing elements. Thedispensing elements can comprise, for example, spray nozzles or beformed as spray nozzles. The spray liquid to be dispensed can be eitherthe main liquid, the liquid active substance mixture, or a mixed liquidwhich is created by remixing the main liquid and the liquid activesubstance mixture. Furthermore, the active substance supply system canbe configured to introduce the main liquid into the one or the severaldistribution sections at several places. The main liquid can there beintroduced into the one or more distribution sections at the same placesas the active substance mixture. Alternatively or in addition, the mainliquid can be introduced into the one or more distribution sections atdifferent places than the active substance mixture.

In a particularly preferred embodiment of the active substance supplysystem according to the invention, the latter comprises several flowcontrol units which are each connected to the main liquid circuit andthe feed system and are configured to control the flow of the mainliquid and the active substance mixture to a distribution section. Theflow control units are preferably switching units, in particularadjustment valves, which open either the flow of the main liquid oralternatively the flow of the active substance mixture to a distributionsection. The flow control units are in particular three-way ball valves.

In a further development of the active substance supply system accordingto the invention, the main liquid circuit comprises in the directionflow downstream of the one or more distribution sections one or morereturn lines which are connected to the reservoir, where a respectiveshut-off device is arranged at the one or more return lines and isconfigured to block the flow. By blocking the flow in the direction ofthe reservoir, it is possible to prevent the liquid active substancemixture from being conveyed back into the reservoir and mixing with themain liquid within the reservoir. If such mixing were to take place,then precise adaptation of the active substance mixture by varying thequantity of active substance added would no longer be possible. The oneor more shut-off devices can be formed, for example, as two-way ballvalves. Arranged between the return lines and the reservoir ispreferably a manifold line so that only one line is to be led back tothe reservoir.

In another embodiment of the active substance supply system according tothe invention, a branching is present at the main liquid circuit andconnects the main liquid circuit to a mixing chamber of the feed systemin a manner conveying liquid. The mixing chamber of the feed system isconnected to a dosing device for the active substance. The dosing devicepreferably comprises a dosing pump for the active substance. The mainliquid is mixed with the active substance in the mixing chamber to formthe liquid active substance mixture. The active substance supply systempreferably comprises a respective flow meter between the branching andthe mixing chamber, in the main liquid circuit between the branching andthe one or more distribution sections and/or in the main liquid circuitbetween the one or more return lines and the reservoir. The quantity ofliquid conveyed to the dispensing elements and the quantity of liquidconveyed back into the reservoir can be determined by the flow meters,so that the current dispensing quantity can be determined.

In a further embodiment of the active substance supply system accordingto the invention, the branching comprises a flow control unit which isconfigured to control the flow of the main liquid circulating in themain liquid circuit and/or the outflow of the main liquid circulating inthe main liquid circuit to the mixing chamber. The flow control unit canbe configured in such a way that the ratio of the flow of the mainliquid circulating in the main liquid circuit and the outflow of themain liquid circulating in the main liquid circuit to the mixing chamberis adjustable. The flow control unit can also be formed as a switchingunit, in particular an adjustment valve, which either permits thecirculation of the main liquid in the main liquid circuit oralternatively redirects the main liquid from the main liquid circuit tothe mixing chamber. The flow control unit is preferably a three-way ballvalve. The active substance supply system preferably comprises a flowmeter between a conveying device of the main liquid circuit and the flowcontrol unit of the branching. The current dispensing quantity can bedetermined by comparing the flow rate toward the dispensing elementswith the return quantity into the reservoir.

In a further development of the active substance supply system accordingto the invention, the latter comprises several flow control units whoseinlets are each connected to the main liquid circuit and preferably notconnected to the feed system and which are each configured to controlthe flow of the main liquid to a distribution section. The flow controlunits are preferably formed as valve units, in particular as checkvalves.

In another embodiment of the active substance supply system according tothe invention, the latter comprises several flow control units whoseinlets are each connected to the feed system and preferably notconnected to the main liquid circuit and which are each configured tocontrol the flow of the active substance mixture to a distributionsection. The flow control units are preferably formed as valve units, inparticular as check valves.

In addition, an active substance supply system according to theinvention is preferred which comprises a circulation circuit for theactive substance mixture that enables circulation of the activesubstance mixture. Due to the circulation circuit for the activesubstance mixture, an active substance mixture with the desired mixingratio is present at the flow control units which are each connected tothe feed system. The circulation within the circulation circuit is firstused to create a homogeneous active substance mixture made up of themain liquid and the active substance. As soon as the homogeneous mixtureof active substances has been created, the circulation of the activesubstance mixture within the circulation circuit prevents the activesubstances from segregating and depositing.

In another embodiment of the active substance supply system according tothe invention, the circulation circuit to the reservoir and/or to theone or more distribution sections can be blocked. Blocking thecirculation circuit to the reservoir prevents the active substancemixture from entering the reservoir and mixing with the main liquid. Bythe fact that the circulation circuit can be blocked from the one ormore distribution sections, dispensing the active substance mixture canbe interrupted without switching the dispensing elements. In addition,blocking the circulation circuit from the one or more distributionsections further enables dispensing pure main liquid, while an activesubstance mixture continues to circulate within the circulation circuit.

In an advantageous further development of the active substance supplysystem according to the invention, the circulation circuit and the mainliquid circuit are completely separable from each other. The circulationcircuit and the main liquid circuit each preferably comprise at leastone separate conveying device, in particular a pump, so that thecirculation within the circulation circuit does not depend on thecirculation within the main liquid circuit. Alternatively, thecirculation circuit and the main liquid circuit can be coupled to eachother, for example, in such a way that the circulation circuit and themain liquid circuit exhibit common line sections. By suitably switchingblocking devices, either a circulation within the circulation circuit ora circulation within the main liquid circuit can be realized in thiscase.

In addition, an active substance supply system according to theinvention is further advantageous in which the circulation circuitcomprises a conveying device and a bypass line bridging the conveyingdevice. The bypass line inlet is arranged in the direction of flowdownstream of the conveying device and the bypass outlet is arranged inthe direction of flow upstream of the conveying device. The bypass lineis preferably used for cleaning and/or emptying the circulation circuit.

The object underlying the invention is further satisfied with anagricultural sprayer of the type mentioned above, where the activesubstance supply system of the agricultural sprayer according to theinvention is formed according to one of the embodiments described above.Regarding the advantages and modifications of the agricultural sprayeraccording to the invention, reference is made to the advantages andmodifications of the active substance supply system according to theinvention.

The object underlying the invention is further satisfied with a methodfor dispensing a spray liquid of the type mentioned above, where themethod of the invention comprises the introduction of the activesubstance mixture into the one or more distribution sections at severalplaces. Regarding the advantages and modifications of the methodaccording to the invention, reference is first made to the advantagesand modifications of the active substance supply system according to theinvention.

The main liquid circuit preferably comprises at least one section of thedistributor linkage, a plurality of dispensing elements, and/or at leastone flow generator. The dispensing elements can there, for example, beformed as spray nozzles or each comprise spray nozzles.

In a preferred embodiment of the method according to the invention, theflow of the main liquid and the active substance mixture to adistribution section is controlled at the several places. Controllingthe flow can comprise, for example, interrupting or opening the flow ofmain liquid and/or active substance mixture.

Furthermore, controlling the flow can also comprise adjusting a volumeor mass flow of the main liquid and/or the active substance mixture.

In addition, a method according to the invention is preferred in whichcontrolling the flow of the main liquid and the active substance mixtureto a distribution section at several places is respectively effectedwith a switching unit, in particular an adjustment valve, which openseither the flow of the main liquid or alternatively the flow of theactive substance mixture to a distribution section. In this way, eitherthe main liquid or the active substance mixture can be introduced intothe one or more distribution sections.

In a further development of the method according to the invention,controlling the flow of the main liquid and the active substance mixtureto a distribution section at the several places is respectively effectedwith separate valves for the main liquid and the liquid active substancemixture. When using separate valves, different quantities of main liquidand/or active substance mixture can be supplied to the differentdistribution sections. Dispensing can be made even more flexible in thisway.

In a particularly preferred embodiment of the method according to theinvention, the latter comprises blocking the return flow of the mainliquid circuit from the one or more distribution sections to thereservoir and/or opening the return flow of the main liquid circuit fromthe one or more distribution sections to the reservoir.

A method according to the invention is further preferred in which theactive substance mixture circulates in a circulation circuit. Thecirculation within the circulation circuit is first used to create ahomogeneous active substance mixture made up of the main liquid and theactive substance. Once the homogeneous mixture has been created, thecirculation of active the substance mixture within the circulationcircuit prevents the active substances from segregating and depositing.

In another embodiment of the method according to the invention, onedistribution section or several or all distribution sections arepreloaded with the active substance mixture before their dispensingelements are opened. Preloading is there done in that the one or moreshut-off devices at the return flow lines remain open and the flowcontrol units supply active substance mixtures to the one distributionsection or to the several or to all distribution sections until theactive substance mixture is present at the dispensing elements of theone distribution section or the several or all distribution sections.

In addition, a method according to the invention is preferred in whichthe circulation circuit is preloaded with an active substance mixturebefore the flow from the circulation circuit to the one or moredistribution sections is opened. Preloading is there done in that thecirculation circuit is supplied active substance until the desiredactive substance mixture in the circulation circuit has been reachedbefore the flow from the circulation circuit to the one or moredistribution sections is opened.

In a further embodiment of the method according to the invention, thespray liquid to be dispensed is changed from the active substancemixture to pure main liquid, where, for changing the spray liquid to bedispensed from the active substance mixture to pure main liquid, the oneor more shut-off devices at the return flow lines remain closed untilall the active substance mixture has left the lines of the main liquidcircuit.

The active substance mixture can also be dispensed at regular orirregular time intervals to prevent the active substance fromdepositing. Furthermore, in order to prevent deposits in the regions ofthe feed system and/or in the region of the circulation circuit, themain liquid can be introduced into the feed system and/or circulatedwithin the circulation circuit if no active substance mixture is to bedispensed for a longer period of time. In addition, the circulationcircuit can comprise its separate conveying device, in particular apump, with which continuous circulation can be implemented, even if noactive substance mixture is removed from the circulation circuit fordispensing. Furthermore, the circulation circuit can be in part orentirely emptied by the pump in the circulation circuit. For entirelyemptying the circulation circuit, the latter preferably comprises abypass line, where the bypass line inlet is arranged in the direction offlow downstream if the conveying device of the circulation circuit andthe bypass outlet is arranged in direction of flow upstream of theconveying device of the circulation circuit. The bypass line can be usedto clean and/or empty the circulation circuit.

Further details of the invention can be gathered from the description ofthe figures and the drawings, where

FIG. 1 shows an embodiment of the active substance supply systemaccording to the invention in a schematic representation; and

FIG. 2 shows a further embodiment of the active substance supply systemaccording to the invention in a schematic representation.

FIG. 1 shows an active substance supply system 10 for an agriculturalsprayer. Active substance supply system 10 comprises a main liquidcircuit 12 within which a main liquid, such as water or a premixed spraybroth, circulates.

Main liquid circuit 12 comprises a reservoir 14 for the main liquid, twoflow meters 16 a, 16 b, several flow control units 18 a-18 c and severaldistribution sections 20 a-20 c. Flow meter 16 a is arranged between abranching 28 and distribution sections 20 a-20 c. Flow meter 16 b isarranged between return lines 24 a-24 c and reservoir 14. Several flowcontrol units 18 a-18 c are each connected to main liquid circuit 12 anda feed system 32, control the flow of the main liquid and an activesubstance mixture to distribution sections 20 a-20 c. The activesubstance mixture and the main liquid can be introduced intodistribution sections 20 a-20 c at several places 68 a-68 c. Flowcontrol units 18 a-18 c are formed as 3-way ball valves. Distributionsections 20 a-20 c each distribute to several dispensing elements 22a-22 c spray liquid to be dispensed.

In the direction of flow downstream of distribution sections 20 a-20 c,main liquid circuit 12 comprises return lines 24 a-24 c which areconnected to reservoir 14. Arranged at each return flow lines 24 a-24 cis a shut-off device 26 a-26 c which is formed as a 2-way ball valvewith which the flow can be blocked. A manifold line is also arrangedbetween return lines 24 a-24 c and reservoir 14.

Branching 28 is further present at main liquid circuit 12 and connectsmain liquid circuit 12 to a mixing chamber 38 of feed system 32 in amanner conveying liquid. Arranged between branching 28 and mixingchamber 38 is a flow meter 30. The main liquid is mixed with the activesubstance in mixing chamber 38 of feed system 32 to form a liquid activesubstance mixture. The active substance is fed via dosing pump 34 andline 36 to mixing chamber 38.

Active substance supply system 10 illustrated can be employed, forexample, in an agricultural sprayer comprising a distributor linkage onwhich dispensing elements 22 a-22 c are arranged.

When spray liquid is dispensed, the main liquid circulates in mainliquid circuit 12 of active substance supply system 10. The main liquidis mixed by feed system 32 with active substance to form a liquid activesubstance mixture and the active substance mixture is introduced intodistribution sections 20 a-20 c at several places 68 a-68 c. Withindistribution sections 20 a-20 c, the active substance mixture isdistributed to dispensing elements 22 a-22 c which ultimately deliverthe active substance mixture as a spray liquid onto agricultural land.The flow rate of the main liquid and the active substance mixture todistribution sections 20 a-20 c is controlled with flow control units 18a-18 c.

Furthermore, distribution sections 20 a-20 c can be preloaded with theactive substance mixture before their dispensing elements 22 a-22 c areopened. Preloading is done in that shut-off devices 26 a-26 c at returnlines 24 a-24 c remain open and flow control units 18 a-18 c supply theactive substance mixture to distribution sections 20 a-20 c until theactive substance mixture is present at dispensing elements 22 a-22 c ofdistribution sections 20 a-20 c.

When changing the spray liquid to be dispensed from the active substancemixture to pure main liquid, shut-off devices 26 a-26 c remain closed atreturn lines 24 a-24 c until all the active substance mixture has leftthe lines of main liquid circuit 12.

FIG. 2 shows an active substance supply system 10 with a main liquidcircuit 12 and a circulation circuit 54.

In the flow direction upstream of distribution sections 20 a-20 c, mainliquid circuit 12 comprises a return line 2 which is connected toreservoir 14, where a shut-off device 26 configured to block the flow isarranged at return line 24. Shut-off device 26 is configured as a 2-wayball valve.

A branching 28 is again present at main liquid circuit 12 and connectsmain liquid circuit 12 to a mixing chamber 38 of feed system 32 in amanner conveying liquid. Branching 28 in this embodiment comprises aflow control unit 52 which is configured to control the flow of the mainliquid circulating in main liquid circuit 12 and/or the outflow of themain liquid circulating in main liquid circuit 12 to mixing chamber 38.Flow control unit 52 is a 3-way ball valve which either permits thecirculation of the main liquid in main liquid circuit 12 oralternatively redirects the main liquid from main liquid circuit 12 tomixing chamber 38. A flow meter 66 is additionally arranged between aconveying device 40 of main liquid circuit 12 and flow control unit 52of branching 28.

Furthermore, main liquid circuit 12 comprises several flow control units62 a-62 c which each control the flow of the main liquid to adistribution section 20 a-20 c.

Circulation circuit 54 permits the circulation of the active substancemixture. Due to circulation circuit 54, an active substance mixture withthe desired mixing ratio is present at flow control units 64 a-64 cwhich are each connected to feed system 32. Flow control units 64 a-64 ceach control the flow of the active substance mixture to a distributionsection 20 a-20 c. Circulation circuit 54 to reservoir 14 anddistribution sections 20 a-20 c can be blocked. Furthermore, circulationcircuit 54 and main liquid circuit 12 are completely separable from eachother. In order to nevertheless maintain circulation, circulationcircuit 54 and main liquid circuit 12 each comprise a separate conveyingdevice 40, 56, each formed as a pump.

Circulation circuit 54 also comprises a bypass line 60 that bridgesconveying device 56. The bypass line inlet is arranged in the flowdirection downstream of conveying device 56 and the bypass outlet isarranged in the flow direction upstream of conveying device 56. Theintegration of bypass line 60 is controlled by flow control unit 58which is configured as a 3-way ball valve. Bypass line 60 is used forcleaning and emptying circulation circuit 54.

The active substance supply system illustrated can also be employed inan agricultural sprayer comprising a distributor linkage on whichdispensing elements 22 a-22 c are arranged.

LIST OF REFERENCE NUMERALS

10 active substance supply system

12 main liquid circuit

14 reservoir

16 a, 16 b flow meters

18 a-18 c flow control units

20 a-20 c distribution sections

22 a-22 c groups of dispensing elements

24, 24 a-24 c return lines

26, 26 a-26 c shut-off devices

28 branchings

30 flow meter

32 feed system

34 dosing pump

36 line

38 mixing chamber

40 conveying device

52 flow control unit

54 circulation circuit

56 conveying device

58 flow control unit

60 bypass line

62 a-62 c flow control units

64 a-64 c flow control units

66 flow meter

68 a-68 c introduction points

The invention claimed is:
 1. Active substance supply system for anagricultural sprayer, comprising: a main liquid circuit which comprisesa reservoir for a main liquid and permits circulation of said mainliquid, where said main liquid circuit comprises one or moredistribution sections which are each configured to distribute to severaldispensing elements a spray liquid to be dispensed, and a feed systemwhich is connected to said main liquid circuit and in which said mainliquid is mixed with at least one separately fed active substance toform a liquid active substance mixture; wherein said active substancesupply system is configured to introduce said liquid active substancemixture into said one or more distribution sections at several places,and wherein a branching is present at said main liquid circuit andconnects said main liquid circuit to a mixing chamber of said feedsystem in a manner conveying liquid.
 2. Active substance supply systemaccording to claim 1, further comprising several flow control unitswhich are each connected to said main liquid circuit and said feedsystem and are configured to control the flow of said main liquid andsaid liquid active substance mixture to a distribution section. 3.Active substance supply system according to claim 1, wherein said mainliquid circuit comprises in the direction of flow downstream of said oneor more distribution sections one or more return lines which areconnected to said reservoir, where a respective shut-off device isarranged at said one or more return lines and is configured to block theflow.
 4. Active substance supply system according to claim 1, whereinsaid branching comprises a flow control unit which is configured tocontrol the flow of said main liquid circulating in said main liquidcircuit or the outflow of said main liquid circulating in said mainliquid circuit to said mixing chamber.
 5. Active substance supply systemaccording to claim 1, further comprising several flow control unitshaving inlets each connected to said main liquid circuit and not to saidfeed system and which are each configured to control the flow of saidmain liquid to a distribution section.
 6. Active substance supply systemaccording to claim 1, further comprising several flow control unitshaving inlets each connected to said feed system and not to said mainliquid circuit and which are each configured to control the flow of saidliquid active substance mixture to a distribution section.
 7. Activesubstance supply system according to claim 1, further comprising acirculation circuit for said liquid active substance mixture whichpermits circulation of said liquid active substance mixture.
 8. Activesubstance supply system according to claim 7, wherein said circulationcircuit to said reservoir or to said one or more distribution sectionsis configured to be blocked.
 9. Active substance supply system accordingto claim 7, wherein said circulation circuit and said main liquidcircuit are entirely separable from each other.
 10. Active substancesupply system according to claim 7, wherein said circulation circuitcomprises a conveying device and a bypass line bridging said conveyingdevice.
 11. Agricultural sprayer, comprising: a distributor linkage onwhich several dispensing elements are arranged; and an active substancesupply system which provides said dispensing elements with a sprayliquid to be dispensed; wherein said active substance supply systemcomprises: a main liquid circuit which comprises a reservoir for a mainliquid and permits circulation of said main liquid, where said mainliquid circuit comprises one or more distribution sections which areeach configured to distribute to said several dispensing elements thespray liquid to be dispensed, and a feed system which is connected tosaid main liquid circuit and in which said main liquid is mixed with atleast one separately fed active substance to form a liquid activesubstance mixture, and where said main liquid circuit is connected to amixing chamber of said feed system by means of a branching present atsaid main liquid circuit in a manner conveying liquid; wherein saidactive substance supply system is configured to introduce said liquidactive substance mixture into said one or more distribution sections atseveral places.
 12. Method for conveying a spray liquid with anagricultural sprayer, comprising the steps of: circulating a main liquidin a main liquid circuit of an active substance supply system of saidagricultural sprayer, said main liquid circuit comprising a reservoirfor a main liquid, distributing to several dispensing elements in one ormore distribution sections of said main liquid circuit a spray liquid tobe dispensed, mixing main liquid with an active substance to form aliquid active substance mixture in a feed system of said activesubstance supply system of said agricultural sprayer, the main liquidcircuit being connected to a mixing chamber of said feed system by meansof a branching present at said main liquid circuit in a manner conveyingmain liquid; and introducing said liquid active substance mixture intosaid one or more distribution sections at several places.
 13. Methodaccording to claim 12, further comprising the step of: controlling theflow of said main liquid and said liquid active substance mixture to adistribution section at said several places.
 14. Method according toclaim 13, wherein controlling the flow of said main liquid and saidliquid active substance mixture to a distribution section at saidseveral places is respectively effected by an adjustment valve, whichopens either the flow of said main liquid or alternatively the flow ofsaid liquid active substance mixture to a distribution section. 15.Method according to claim 13, wherein controlling the flow of said mainliquid and said liquid active substance mixture to a distributionsection at said several places is respectively effected with separatevalves for said main liquid and said liquid active substance mixture.16. Method according to claim 12, further comprising the steps of:blocking the return flow of said main liquid circuit from said one ormore distribution sections to said reservoir; opening the return flow ofsaid main liquid circuit from said one or more distribution sections tosaid reservoir.
 17. Method according to claim 12, further comprising thestep of: circulating said liquid active substance mixture in acirculation circuit.
 18. Method according to claim 17, furthercomprising the step of: preloading said circulation circuit with saidactive substance mixture before the flow from said circulation circuitto said one or more distribution sections is opened.
 19. Methodaccording to claim 12, further comprising the step of: preloading onedistribution section, several or all distribution sections with saidliquid active substance mixture before their dispensing elements areopened.
 20. Method according to claim 12, further comprising the stepof: changing said spray liquid to be dispensed from the active substancemixture to pure main liquid, wherein, for changing said spray liquid tobe dispensed from the active substance mixture to pure main liquid, saidone or more shut-off devices remain closed at said return lines untilall the active substance mixture has left the lines of said main liquidcircuit.